Control system for an alarm installation having a remote transmitter with a remotely controlled emergency device

ABSTRACT

A control system for use with emergency devices utilizes an alarm installation having a plurality of transmitters and a single common receiver. Each transmitter is provided with a &#39;&#39;&#39;&#39;memory&#39;&#39;&#39;&#39; contact which remains closed after the transmitter has generated an alarm signal. An oscillating control voltage is fed from the receiver through the contact to actuate an emergency device at any time after the alarm signal. The memory contact is reset by sending from the receiver a reset pulse voltage having an &#39;&#39;&#39;&#39;on&#39;&#39;&#39;&#39; period longer than that of the control voltage.

United States Patent 1 91 1111 3,840,871 Eguchi et al. v Oct. 8, 1974[54] CONTROL SYSTEM FOR AN ALARM 3,585,620 6/1971 Durand 340 222INSTALLATION HAVING A REMOTE 3,588,893 6/1971 McCloskey TRANSMITTER WITHA REMOTELY 3,643,244 2/1972 Levy 340/4l8 CONTROLLED EMERGENCY DEVICE[75] Inventors: Yoshihiro Eguchi; Yasaburo Adachi; 'f h CaldwellKatsutoshi Kuwabara an of Tokyo, Assistant Exammer-ihchard P. Lang JapanAttorney, Agent, or FzrmLane, Aitken, Dunner &

- Ziems [73] Assignee: Hochiki Corporation, Tokyo, Japan [22] Filed:Dec. 19, 1972 21 App]. No.: 316,460 [57] ABSTRACT A control system foruse with emergency devices uti- [30] Foreign Application P i it D tlizes an alarm installation having a plurality of transoecr 29 1971Japan 46-3239 miners and a Single common receive Each transmit ter isprovided with a memory contact which re- [52] US 340/310 R 340/213 R340/418 mains closed after the transmitter has generated an 340/289alarm signal. An oscillating control voltage is fed from 511 Int. Cl. .Q..-H04m 11/04 the receiver through the t actuate 5 Field of Search 340310 2 3 R 41 227 gency device at any time after the alarm signal. The

340/228 222 169/2 R memory contact is reset by sending from the receivera reset pulse voltage having an on period longer [56] References Citedthan that of the control voltage.

UNITED PATENTS 12 Claims, 2 Drawing Figures 3,508,233 4/1970 sugiyama340/222 1 l RESET m 1 SELF-HOLDlNG /"l CONTACT 411 I l LAY LALARM REENSING 1Q ELgigENT 1 4 1 .i- I I D l 1 R SET 15 J PAIENTEDBBI 81974$840,871

l 6 v F G2 CONTROL EMERGECSVCY DEVICE SWITCH 7 RESET 4 KEY A I T RELAYii E CONTACT P R6 24o SELF*HOLDING I I 2 CONTACT 4a /TRANSM ITTER 2O lSET CONTROLLED 3 com DEVICE 24 (RELAY) :/26T1 E' R Z 8 R ENSlNG ELEMENTg 2-- Rgz; R D4 I T 10 4 E IE R I J CONTROL SYSTEM FOR AN ALARMINSTALLATION HAVING A REMOTE TRANSMITTER WITH A REMOTELY CONTROLLEDEMERGENCY DEVICE BACKGROUND OF THE INVENTION This invention relates to acontrol system which utilizes an alarm installation for signaltransmission. Typical fire alarm systems employ a plurality oftransmitters stationed at different points in a building, for example,and a single common receiver at another location. Each transmitter isconnected by wire to the receiver and sends an alarm signal when it hasdetected an abnormal enviromental state such as smoke or extreme heat.The receiver sounds an alarm upon receipt of the alarm signal. Alarminstallations of this type, in general, are used exclusively forgenerating an alarm and are rarely used for any other purpose. Moresophisticated fire alarm systems will be needed in the future to copewith the increasing size and complexity of modern buildings. Besidesalarms, large buildings should be provided with emergency fire controland safety devices such as guide lamps, emergency exit lamps, fireshutters, smoke shutters, and smoke exhaust fans as well as fireextinguishers. If the existing fire alarm installation could be partlyutilized to control these emergency devices, automatically controlledoperation of the system could be achieved at relatively low cost.

Emergency equipment is usually designed to be activated at the firstsign of fire. However, such equipment should not always be actuatedimmediately when a fire breaks out. For example, a fire shutter shouldnot be closed with a person trapped in a room, and smoke exhaust fansneed not always be started even though a room has been evacuated. Theseemergency devices should not be linked directly to fire detectors butshould be actuated selectively upon proper judgement of the situation ata central receiving station.

An indicator lamp is sometimes installed at the transmitter site toprovide a convenient means for identifying the transmitter which hasgenerated the alarm signal as well as for operational tests. Theusefulness of the lamp may be enhanced if it is lighted only when it isreally required or is cyclically flickered in order to be moreconspicuous to the human eye. In conventional alarm systems, however,the lamp is turned on continuously when the transmitter is actuated.

SUMMARY OF THE INVENTION A control system which utilizes an alarminstallation according to the invention is provided with a memory"contact which is adapted to be closed in response to the operation of atransmitter. The contact remains closed until a reset voltage isreceived. By supplying a control voltage from the receiver to thecontrolled device via the memory contact, the device can be actuatedwhenever required.

The control system according to the present invention can accomplish thereset operation by employing a reset voltage which is of the samepolarity as that of the control voltage but has a longer on period thanthat of the control voltage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagramillustrating an example of a control system of the present invention.

FIG. 2 is a schematic circuit diagram illustrating an example of acontrolled device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, areceiver 10 comprises a power supply 2, an alarm relay 4, an oscillator6, a transistor switching circuit 12 responsive to the oscillator 6, anda relay 8 controlled by the circuit 12. One end of the power supply 2 isconnected to a terminal I, of the receiver through a stationary contact8b and a moving contact of the relay 8, and the other end thereof isconnected to a terminal of the receiver through a reset key K2 and thealarm relay 4. The contacts 8b and 8c are normally closed. The relay 8also has a stationary contact 8a which is connected to the other end ofthe power supply 2 through a resistor R1. A control switch K, operatesthe oscillator 6 which may be a multivibrator or other conventional typeof oscillator. When the control switch K, is closed, the oscillator 6 isenergized by the power supply 2 and generates a rectangular pulsevoltage consisting of an on period and an off period. The generatedvoltage of rectangular wave shape is produced at output terminals t andof the oscillator 6. The switching circuit 12 includes transistors Tr,.and Tr The collector of the transistor Tr, is connected to the emitterof the transistor Tr through a register R and the emitter of thetransistor Tr is connected to the terminal t which is connected to oneend of the power supply 2. The terminal 2 is connected to the other endof the power supply 2 through a resistor R The base of the transistorTr, is connected to the output terminal t of the oscillator 6 and alsois connected to a capacitor C, through a resistor R and a diode D,. Thejunction of the, capacitor C, and diode D, is connected to one end ofthe power supply 2 through a reset key K and the other end of thecapacitor C, is connected to the other end of the power supply 2. Thebase of the transistor Tr, is connected to the collector of thetransistor Tr, through a resistor R and the collector of the transistorTr, is connected to the other end of the power supply 2 through the coil8d of the relay 8.

A pair of external lead wires 1, and 1 are connected to terminals t, andt of the receiver, and the lead wires l, and 1 run a transmitter 20representative of a plurality of similar transmitters installed inmonitored areas.

The transmitter 20 has a diode bridge 22, a controlled device 24, anoperation memory contact 26a and a reset circuit 40 therefor, athyristor switching element SCR,, and asensing element or detector32.-The input terminals of the diode bridge 22 are connected to the leadwires 1, and I, through the transmitter terminals t and t.,, and theoutput terminals of the diode bridge 22 are connected to bus wire linesI and 1 in the transmitter 20. Due to the function of the diode bridge22, the polarity of the voltage which appears at the bus wires 1 and l,is constant irrespective of connection polarities of the lead wires 1,and 1 to the transmitter 20, thereby preventing erroneous operation ofthe transmitter 20. As shown in FIG. 2, the controlled device 24, inthis example, is a relay which has a contact 24a adapted to control anemergency device 30 which may be a guide lamp, a fire shutter, a smokeexhaust fan, or other device. Alternatively, an indicator lamp toindicate the operation of the transmitter 20 may be used instead of arelay for use in the controlled device 24.

' The operation memory contact 26a is preferably a contact of a latchingrelay 26 which has a set coil Rp and a reset coil Rs. Turning to the setcircuit, the set coilRp is connected between the bus wires 1 and 1 inseries with a diode D a capacitor C and a resistor R A resistor R isconnected in parallel with the set coil Rp and the diode D In the resetcircuit 40, the reset coil Rs is connected between the bus wires 1 andin series with the memory contact 260, a diode D and a thyristor SCR Acapacitor C is connected in parallel to the thyristor SCR and the resetcoil Rs. The trigger electrode of the thyristor SCR is connected to thebus wire 1 through a resistor R and also is connected to a triggeringcapacitor C through a zener diode Z The capacitor C is connected to thebus wire 1 through the parallel circuit consisting of a resistor R and adiode D and through the memory contact 26a.

A sensing element 32 is used to provide an output signal in response tochange in the environmental condition. A conventional type of sensor maybe used for the sensing element 32. One end of the thyristor SCR isconnected to the bus wire 1 and the other end of the thyristor SCR, isconnected to the bus wire 1., through a capacitor C The capacitor C isconnected to the resistor R through a diode D Under the normal monitoredenvironmental condition, the power supply 2 of the receiver suppliespower through the lead wires 1, and 1 to the bus wires 1 and 1 When firebreaks out, the sensing element 32 produces an output signal with whichthe thyristor SCR is triggered and driven into the on state. Thecapacitor C which is connected in series with the thyristor SCR normallyis discharged through the resistor R When the output signal is appliedfrom the sensing element 32, the lead wires 1 and 1 are short-circuitedwith the thyristor SCR, and the capacitor C and, consequently, the alarmrelay 4 in the receiver 10 is energized to generate an alarm signal andto close its selfholding contact 4a. In the transmitter, the capacitorC, is normally charged by the bus wires 1 and I, through resistors R andR When an output signal is applied from the sensing'element 32 and thethyristor SCR, is driven into the on state, the charge of the capacitorC is discharged through the circuit consisting of the diode D the setcoil Rp, the thyristor SCR, and the diode D thereby energizing the setcoil Rp of the latching relay. Consequently, the contact 26a is closedand the controlled device 24 alone is connected to the bus wires 1 and 1However, because the self-holding contact 4a of the alarm relay 4 isclosed, the lead wires 1, and 1 are short-circuited and provide novoltage and, therefore, the controlled device 24 is not energized.

For the controlled device 24 in this example, a relay coil of the slowreleasing type is employed. For actuating the controlled device 24, thecontrol switch K, of the receiver 10 is closed. When the switch K, isclosed, the oscillator 6 generates a pulse signal whose on period isshorter than its off period. This pulse signal is applied to thetransistor Tr from the terminal As the pulse signal is applied, thetransistor Tr, energizes the relay 8 intermittently via the transistorTr thereby switching its movable contact 8c between its stationarycontacts 8a and 8b repeatedly. When the contact is thrown into contactwith the contact 8a, a negative voltage is supplied to the lead wire 1and a positive voltage is applied to the lead wire 1 energizing thecontrolled device 24 at the transmitter site. The contact 24a (FIG. 2)is closed thereby starting the actuating motor, for example, of theemergency device 30. Since a slow releasing relay is used for thecontrolled device 24 which is intermittently energized, its contact 24ais prevented from synchronous on-off operation. However, if an indicatorlamp is used in place of the controlled device 24, the lamp is on-offcontrolled with the control voltage to indicate the operating state.

When the voltage is intermittently applied to the lead wires 1 and 1 thebus wires 1 and 1 are not shortcircuited by the thyristor SCR even ifvit is turned on by the output of the sensing element 32. This is becausethe capacitor C has already been charged or is instantaneously chargedwhen the voltage is applied.- The capacitor C of the reset circuit 40 isenergized when the voltage is intermittently fed to the lead wires 1,and 1 However, the terminal voltage of the capacitor C does not rise toa sufficiently high level to break down the zener diode 2 because thecharge of the capacitor C is discharged through the diode D and thecontrolled device 24 during the off period of the pulse voltage.

The memory contact 26a can be reset by momentarily closing the reset keyK, of the receiver 10. When the reset key K is closed the capacitor C ischarged with the voltage of the power supply 2. The charge of thecapacitor C is discharged through the circuit consisting of the diodeD,, the resistor R the base and emitter of the transistor Tr plus theresistors R and R During the period for which the discharge currentflows, the relay 8 is kept energized and its moving contact 80 is keptin contact with its stationary contact 8a for a longer period of time,thereby providing a pulse current of a wider pulse width or on period tothe transmitter 20. The capacitor C of the transmitter 20 is charged fora longer period of time and the terminal voltage of the capacitor 20ultimately reaches a level sufficiently high to drive the zener diode 2into the reverse conducting state. As the zener diode Z becomesconductive, the thyristor SCR is triggered into the conducting state andconsequently the reset coil Rs is energized. As a result, the memorycontact 260 is reset or opened and the controlled device 24 isde-energized or turned off.

As described above, this invention provides means to selectively controlemergency devices which are related to alarm-generating sensors, simplyby adding to an already-installed fire alarm installation, theoscillator circuit 6, the controlled device 24, the memory contact 26a,and the reset circuits 28 and 40 for use with the memory contact 26a. Itis possible to automati cally start the emergency device by driving thecontrol switch K with the alarm relay 4, if desired. Simultaneousresetting of the alarm relay 4 and the controlled device 24 can beachieved by breaking the reset key K (HQ. 1). Since the contact 260memorizes" that the sensing element 32 has generated an alarm, thememory contact 26a is not reset even when the lead wires 1, and I arede-energized and, therefore, the controlled device can be immediatelyoperated when the control pulse is supplied.

Thus, the circuit described above can be easily adapted to performdifferent operations, for example: selective remote activation anddeactivation of emergency equipment; automatic activation and selectiveremote deactivation of equipment; and automatic or selective remoteactivation and deactivation of a flickering indicator light or othersignal means at the transmitter site. This versatility allows a varietyof uses of the same alarm system. The system is shown in connection withfire detection apparatus only for illustration, and is similarlyapplicable where conditions other than fire, such as nuclear radiation,are being monitored at a central station with one or more detectionsites.

The present invention is not limited to the above illustrated examplebut can be embodied in various ways within the scope and spirit of theappended claims.

We claim:

1. A control system for an alarm installation equipped with a receiveradapted to be connected to a power supply and having alarm relay means,and a remote transmitter connected through lead wires to said receiver,said transmitter having a sensing element for detecting an abnormalcondition and a switching element to actuate said alarm relay means insaid receiver by connecting said lead wires, wherein the improvementcomprises: said receiver including a self-holding alarm relay contactresponsive to actuation of said alarm relay means to connect said leadwires and means for selectively introducing a control voltage and adifferent reset voltage into said lead wires, and said transmitterincluding a controlled device and a memory switch serially connectedbetween said lead wires, a latching relay responsive to detection bysaid sensing element for closing said memory switch to connect saidcontrolled device between said lead wires to receive said controlvoltage when introduced, said latching relay holding said memory switchclosed until said reset voltage is introduced by said receiver, saidcontrol voltage operating said controlled device without opening saidmemory switch.

2. The control system of claim 1, further comprising an indicator lampwhich serves as said controlled device.

3. The control system of claim 1, further comprising a slow releasingrelay having a contact to control an emergency device which serves assaid controlled device.

4. A control system utilizing an alarm installation, comprising areceiver adapted to be connected to a power supply and having alarmrelay means; a sensing element located remotely from said receiver fordetecting an abnormal condition; two lead wires connecting said sensingelement to said receiver; and a transmitter which has a thyristorresponsive to said sensing element to connect said lead wires to drivesaid alarm relay means; said receiver having a self-holding alarm relaycontact responsive to said alarm relay means for deenergizing said leadwires and said receiver having means to introduce-into said lead wiresapulse control voltage consisting of alternately repeated on and offperiods and also to introduce a reset voltage, the on period of which islonger than that of said pulse control voltage, said transmitter havinga capacitor which is connected in series with said thyristor to cut offsaid thyristor after being charged, a discharge resistor which isconnected in parallel with said capacitor, a slowreleasing relay whichcontrols an emergency device,

and a memory contact which closes when said thyristor is driven into theconductive state bysaid sensing ele ment for connecting said slowreleasing relay to said lead wires until said reset voltage is applied.

5. The control system of claim 4, wherein said transmitter has alatching relay with a setting coil, a resetting coil and a contactserving as said memory contact, said set coil closing said memorycontact when said set coil is energized by the discharge current of saidcapacitor when said lead wires are connected by said thyristor, anotherthyristor interconnecting said memory contact and said resetting coilwith said lead wires, said resetting coil being energized to open saidmemory contact when said other thyristor is driven into the on state,and a trigger capacitor for driving said other thyristor above apredetermined level by said reset voltage.

6. The control system of claim 4, wherein said means of introducing saidpulsed control voltage and said reset voltage includes a control relaywith a coil and a relay contact for cutting out a certain section ofsaid lead wires and connecting the power supply to the cutout section,an oscillator for supplying control voltage to said control relay coil,a control switch for operating said oscillator, a reset capacitor forsupplying reset voltage to said control relay coil, and reset switchmeans for charging said reset capacitor.

7. A control system for selectively energizing a controlled devicethrough an alarm installation, comprising a receiver having alarm relaymeans, a remote transmitter having a detector for producing an alarmsignal indicative of an abnormal condition and switch means responsiveto said alarm signal, an electrical circuit between said transmitter andreceiver interconnecting said alarm relay means andsaid switch means,said switch means closing said circuit in response to said alarmsignalto energize said alarm relay means, said transmitter havingamemory switch for interconnecting the controlled device to said circuitin response to said alarm signal, said receiver having means responsiveto said alarm signal for de-energizing said circuit without deactivatingsaid alarm relay means to prevent said alarm signal from directlyactivating said controlled device, and said receiver having means forselectively energizing and de-energizing said controlled device via saidcircuit and said memory switch.

8. The system of claim 7, wherein said means for energizing andde-energizing said controlled device produces in said circuit a firstpulse voltage having a regular on period to activate said controlleddevice.

9. The system of claim 8,'further comprising slow release relay meansfor interconnecting said memory switch means and the controlled devicesuch that the controlled device is continuously activated by said firstpulse voltage. 7

10. The system of claim 8, wherein said energizing and de-energizingmeans produces in said circuit a second pulse voltage having an onperiod longer than that of said first pulse voltage, said receiverhaving means nonresponsive to said first pulse voltage for reopeningsaid memory switch in response to said second pulse voltage to turn offthe controlled device.

11. A control system for an alarm installation, comprising a receiverwith a self-holding alarm relay. a remote transmitter with a controlleddevice and means for generating an alarm signal, electrical lead wiresinterconnecting said receiver and transmitter, said transmitter havingmeans responsive to said alarm signal for operatively connecting saidlead wires to activate said alarm relay in said receiver, saidtransmitter having latching relay switch means responsive to said alarmsignal for simultaneously connecting said controlled device in circuitwith said lead wires, said latching relay switch means being resettableto disconnect said controlled device in response to a reset voltagepulse of predetermined minimum duration, means in said receiverresponsive to said alarm relay for simultaneously tively connected tosaid slow-releasing relay such thatsaid pulsed control voltage is ofsufficiently short period to keep said emergency device continuouslyenergized via said slow-releasing relay without resetting said latchingrelay switch means.

1. A control system for an alarm installation equipped with a receiveradapted to be connected to a power supply and having alarm relay means,and a remote transmitter connected through lead wires to said receiver,said transmitter having a sensing element for detecting an abnormalcondition and a switching element to actuate said alarm relay means insaid receiver by connecting said lead wires, wherein the improvementcomprises: said receiver including a self-holding alarm relay contactresponsive to actuation of said alarm relay means to connect said leadwires and means for selectively introducing a control voltage and adifferent reset voltage into said lead wires, and said transmitterincluding a controlled device and a memory switch serially connectedbetween said lead wires, a latching relay responsive to detection bysaid sensing element for closing said memory switch to connect saidcontrolled device between said lead wires to receive said controlvoltage when introduced, said latching relay holding said memory switchclosed until said reset voltage is introduced by said receiver, saidcontrol voltage operating said controlled device without opening saidmemory switch.
 2. The control system of claim 1, further comprising anindicator lamp which serves as said controlled device.
 3. The controlsystem of claim 1, further comprising a slow releasing relay having acontact to control an emergency device which serves as said controlleddevice.
 4. A control system utilizing an alarm installation, comprisinga receiver adapted to be connected to a power supply and having alarmrelay means; a sensing element located remotely from said receiver fordetecting an abnormal condition; two lead wires connecting said sensingelement to said receiver; and a transmitter which has a thyristorresponsive to said sensing element to connect said lead wires to drivesaid alarm relay means; said receiver having a self-holding alarm relaycontact responsive to said alarm relay means for de-energizing said leadwires and said receiver having means to introduce into said lead wires apulse control voltage consisting of alternately repeated on and offperiods and also to introduce a reset voltage, the on period of which islonger than that of said pulse control voltage, said transmitter havinga capacitor which is connected in series with said thyristor to cut offsaid thyristor after being chargeD, a discharge resistor which isconnected in parallel with said capacitor, a slow-releasing relay whichcontrols an emergency device, and a memory contact which closes whensaid thyristor is driven into the conductive state by said sensingelement for connecting said slow releasing relay to said lead wiresuntil said reset voltage is applied.
 5. The control system of claim 4,wherein said transmitter has a latching relay with a setting coil, aresetting coil and a contact serving as said memory contact, said setcoil closing said memory contact when said set coil is energized by thedischarge current of said capacitor when said lead wires are connectedby said thyristor, another thyristor interconnecting said memory contactand said resetting coil with said lead wires, said resetting coil beingenergized to open said memory contact when said other thyristor isdriven into the on state, and a trigger capacitor for driving said otherthyristor above a predetermined level by said reset voltage.
 6. Thecontrol system of claim 4, wherein said means of introducing said pulsedcontrol voltage and said reset voltage includes a control relay with acoil and a relay contact for cutting out a certain section of said leadwires and connecting the power supply to the cut-out section, anoscillator for supplying control voltage to said control relay coil, acontrol switch for operating said oscillator, a reset capacitor forsupplying reset voltage to said control relay coil, and reset switchmeans for charging said reset capacitor.
 7. A control system forselectively energizing a controlled device through an alarminstallation, comprising a receiver having alarm relay means, a remotetransmitter having a detector for producing an alarm signal indicativeof an abnormal condition and switch means responsive to said alarmsignal, an electrical circuit between said transmitter and receiverinterconnecting said alarm relay means and said switch means, saidswitch means closing said circuit in response to said alarm signal toenergize said alarm relay means, said transmitter having a memory switchfor interconnecting the controlled device to said circuit in response tosaid alarm signal, said receiver having means responsive to said alarmsignal for de-energizing said circuit without deactivating said alarmrelay means to prevent said alarm signal from directly activating saidcontrolled device, and said receiver having means for selectivelyenergizing and de-energizing said controlled device via said circuit andsaid memory switch.
 8. The system of claim 7, wherein said means forenergizing and de-energizing said controlled device produces in saidcircuit a first pulse voltage having a regular on period to activatesaid controlled device.
 9. The system of claim 8, further comprisingslow release relay means for interconnecting said memory switch meansand the controlled device such that the controlled device iscontinuously activated by said first pulse voltage.
 10. The system ofclaim 8, wherein said energizing and de-energizing means produces insaid circuit a second pulse voltage having an on period longer than thatof said first pulse voltage, said receiver having means nonresponsive tosaid first pulse voltage for reopening said memory switch in response tosaid second pulse voltage to turn off the controlled device.
 11. Acontrol system for an alarm installation, comprising a receiver with aself-holding alarm relay, a remote transmitter with a controlled deviceand means for generating an alarm signal, electrical lead wiresinterconnecting said receiver and transmitter, said transmitter havingmeans responsive to said alarm signal for operatively connecting saidlead wires to activate said alarm relay in said receiver, saidtransmitter having latching relay switch means responsive to said alarmsignal for simultaneously connecting said controlled device in circuitwith said lead wires, said latching relay switch means being resettableto disconnect said controlled Device in response to a reset voltagepulse of predetermined minimum duration, means in said receiverresponsive to said alarm relay for simultaneously de-energizing saidlead wires, said receiver having means for generating said reset voltagepulse, and said receiver having means for introducing on said lead wiresan intermittent regularly repeating pulsed control voltage having an onperiod less than said predetermined minimum duration for said resetvoltage pulse to operate said controlled device on command.
 12. Thecontrol system of claim 11, wherein said controlled device includes aslow-releasing relay connected in circuit with said lead wires by saidlatching relay switch means and an emergency device operativelyconnected to said slow-releasing relay such that said pulsed controlvoltage is of sufficiently short period to keep said emergency devicecontinuously energized via said slow-releasing relay without resettingsaid latching relay switch means.